The Fed is building up a buffer as the economy continues to exhibit requisite growth, so they have ammunition to combat future economic downturns.
Monetary normalization however cannot come at the expense of real future growth expectations. The Fed pays close attention to the real yield curve, which has steepened dramatically this year:
real Treasury yields
In the beginning of January 2016, the spread between the 30 year and 5 year inflation indexed treasury was 83 basis points. As of yesterday, that is as narrow as 11 basis points, which is a signal the yield curve is in danger of inverting.
Furthermore, a critical mass has been reached as the Fed removed language from their statement that has been there since the economic downturn; they no longer label current monetary policy as accommodative. The neutral Fed Funds rate, which is the FFR that is neither accommodative or tight is assumed to be between 2% and 2.5%. U.S. GDP growth will need to maintain our current pace in order for rate increase schedules not to induce some extreme financial volatility.